A defining characteristics of biological signaling is that it is both robust and versatile: the system can respond to a wide variety of inputs and consistently generate outputs specific to each input. This gives the ability for biological systems to adapt to complex environments for optimal fitness. How such robustness and versatility are achieved at once, however, has not been well understood. One effective strategy would be to spatially contain specific signaling modules in specific structures. As such, signaling specificity is ensured by putting specific upstream and downstream components in the same space, and versatility is achieved with the large number of component and structure combinations.